As the demand for plastic materials has increased, efforts have been made to recycle the plastics. Particularly, waste plastics are buried into the ground, or incinerated, but these methods cause soil contamination and air pollution. Accordingly, recently, researches to recycle them have been carried out to such a degree that some methods have attained to a practical stage.
Plastics are very much diversified in their kinds, and different recycling methods have to be employed for different kinds. Among the plastic articles, the plastic containers which contain lubricants are very difficult to recycle. These kinds of plastic containers are contaminated with a high viscosity lubricant component and, therefore, it is difficult to remove the contamination materials. If the temperature is raised to regenerate them, then foul toxic odors are typically generated. Accordingly, so far, a limited amount of waste lubricant containers has been regenerated into low quality products, while the rest of them has been buried or incinerated.
Generally, lubricant contains petroleum substance and additives. The additives contain phenols, zinc compounds, sulphur and its compounds, and calcium/magnesium compounds. All these substances are the causes of contaminations. Lubricants are usually packed in the amount of 2 L, 4 L, and 6 L. The lubricant containers have been mostly buried or incinerated as described above. The lubricant containers are made of polypropylene (PP), or a high density polyethylene (HDPE).